Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h,w=map(int,input().split())
s=[input() for _ in range(h)]
vi=[ [-1 for _ in range(w)] for _ in range(h)]
st=deque()
st.append([0,0,0])


d=[[0,1],[-1,0],[1,0],[0,-1]]
while st:
  h1,w1,i=st.popleft()

  if 0<=h1<h and 0<=w1<w and vi[h1][w1]==-1 and s[h1][w1]==".":
    vi[h1][w1]=i+1
    for m in d:
      st.append([h1+m[0],w1+m[1],i+1])

print("".join(s).count(".")-vi[h-1][w-1] if vi[h-1][w-1]!=-1 else -1)